Piston for combustion power engines



p 1942- F. R. DIETRICH PISTON FOR COMBUSTION POWER ENGINES Filed April 16, 1941 I! III \NVE -me,

Fried rich RI ch arBfeTflch Patented Sept. 29, 1942 UNITED. STATES PATENT OFF-ICE 2,297,460 PISTON Fon COMBUSTION rowan ENGINES Friedrich Richard Dietrich, Munich, Germany; vested in the Alien Property Custodian Application April 16, 1941, Serial No. 388,750

In Germany July 14, 1939 1 Claim.

A known piston of this kind consists of light metal and possesses a thin coat of hard metal e, g. of grey pig iron, which is sprayed on.

In itself such a piston would be suitable to comply with the demands made, if it were not for the coat of hard metal within the range of the ring portion being cut by the ring grooves, with the result that a plurality of separate ring parts are formed which are not anchored in the light metal, so that they are unable to bear the immense strain.

The present invention has for its object to provide a construction with which the thin coat of hard metal is no longer divided into several separate rings, in spite of the ring grooves cutting in.

The invention consists in a thin-walled coat of the piston bearing within the range of the ring portion, and having on the inner circumference ribs running approximately parallel to the longitudinal axis of the piston and lined by the light metal, the depth of said ribs being greater than that of the piston ring grooves. I

The attached drawing shows three forms of execution of the piston according to the invention in which Figure 1 shows a piston in elevation with partial longitudinal section,

Figure 2 a section on line AB oi. Figure 1,

Figure 3 another form of execution of the piston in axial section,

Figure 4 another form of execution in elevation and partial longitudinal section.

The piston 6 as well as its pin bosses 2 consist of light metal. The piston is provided with a thin-walled surface coat 8 of hard metal e. g. of grey pig iron. Within the range of the ring portion the thin-walled coat 5 possesses at its inner circumference a plurality of ribs 3 running parallel to the longitudinal axis of the piston, which ribs in the present instance run longitudinally in the piston head. The light metal i cast subsequently into the preformed shell coat i, fills in the spaces between the ribs 3, a firm mutual connection remaining thereby between thelight metal 4, and the thin-walled coat i and its ribs 3 respectively. The depth of the ribs 3 is greater than that of the piston ring grooves, so that the separate rings of coat I formed by the piston ring grooves are in mutual connection over the ribs 3, and are firmly anchored in the light metal, as shown in Fig. 2.

The piston is conveniently manufactured in such a manner that first the coat I with the ribs 3 appertaining to it is cast in excess diameter, then the coat is turned ofi with excess centrally to the middle axis for insertion into the mould,

whereupon the coat with the ribs is inserted into the mould axially to fit, and then the coat I is lined with the light metal 4 in the manner known to the art.

The piston manufactured in this manner is still unfinished, it must therefore be smooth finished, particularly turned oil to the required diameter.

The form Fig. 4, differs from the form Fig. 1 in not having the thin walled coat I cover the light metal of the piston crown.

The form Figure 4 shows that the light metal skirt of the piston may have a slit 5, so as to take into account the greater possibilities of expansion of the light metal as compared to hard metal in case of larger dimensions.

The piston thus possesses all the advantageous properties of the hard metal piston as well as those of the light metal one; the thin-walled coat is not subdivided into several rings by the piston ring grooves owing to the thin-walled coat being firmly anchored in the light metal over the ribs 3. There is no appreciable increase in the dimension of the piston ring grooves due to expansion o! the ribs 3. Nevertheless the piston rings are in contact with the light metal between the ribs 3, a good thermal conduction being obtained thereby.

To prevent accumulation of heat in the piston head and to endow the piston with a higher thermal conductivity the ribs 3 may be conveniently formed without any, upper mutual connection. This form is shown in Fig.3. For this reason, the piston head is not provided with the coat I, but consists exclusively of light metal.

What I claim is:

A piston for internal combustion engines consisting oi an outer thin-walled coat of hard metal around a light metal piston, the coat possessing within the range of the ring portion ribs at the inner circumference, the ribs running approximately parallel to the longitudinal axis of the piston and lined with the light metal, and the depth of the ribs being greater than that of the ring grooves of the piston.

FRIEDRICH RICHARD DIETRICH. 

